Unveiling the correlation between elemental composition, fermi-level splitting, and charge collection in perovskite solar cells (PSCs) exposed to different environments is crucial to understanding the origin of defects. This will enable defect engineering to achieve high performing and long lasting perovskite solar cells. In this contribution we measured for the first time the spatial distribution and charge collection efficiency at the nano-scale by synchrotron-based x-ray fluorescence (XRF) and x-ray beam induced current (XBIC) with sub-grain resolution, and we observe a correlation between Pb/I ratio and charge collection efficiency. In contrast to other thin-film solar cells, perovskite solar cells are highly sensitive to ambient conditions (atmosphere and illumination). As the XRF and XBIC measurements were conducted in vacuum under an x-ray source illumination, the impact of measurement conditions on the measurements need to be taken into account. Furthermore, necessary conditions for quantification of XRF/XBIC measurements are not fulfilled for perovskite solar cells. Therefore, we will discuss fundamentals of XRF/XBIC measurements of perovskite solar cells that will enable reliable quantitative, high-resolution measurements of elemental distribution and charge collection.